Recently, a biometric authentication technique has been developed for authenticating users of a system in a non-contact manner based on biometric images which represent biometric information such as a venous pattern of hands or fingers, patterns of fingerprints or palms. A biometric authentication apparatus using the biometric authentication technique checks input biometric information of the users against pre-registered biometric information of registered users. The biometric authentication apparatus regards the user whose biometric information corresponds to the registered biometric information as a registered user who has authorized rights, and permits the user to use the system. The biometric authentication apparatus may be incorporated in the system, for example, or externally connected to the system.
The biometric authentication apparatus is used in various fields, such as management of logging on of PCs (Personal Computers), authentication at ATMs (Automated Teller Machine) of banks, management of entrance and exit at offices, etc.
In order to check the users with high accuracy with the biometric authentication apparatus, it is desired that contractual features of the biometric information are clearly captured in the biometric image. Therefore, a biometric authentication sensor for capturing the biometric information to generate the biometric image may include, in addition to an imaging optical system with which a subject including the biometric information such as a hand is captured by an imaging lens and an imaging element such as a CCD (Charge Coupled Device), an illumination optical system for illuminating the subject.
A technique for the biometric authentication sensor including the illumination optical system and the imaging optical system is proposed (Patent Documents 1, 2 and 3, for example).
[Patent Document 1] Japanese Laid-open Patent Publication No. 2009-31903
[Patent Document 2] Japanese Laid-open Patent Publication No. 2013-130981
[Patent Document 3] Japanese National Publication of International Patent Application No. 2005-527874
According to the conventional methods, it is difficult to uniformly illuminate the subject such as a hand with the illumination optical system.